MOLECULAR AND SOLID STATE PHYSICS

Research in the Molecular Physics Laboratory is focused on the discovery and characterization of novel molecular species that are important to a wide variety of fundamental and applied problems in physics, chemistry and astrophysics. These range from the most basic, understanding the transition from molecular to bulk properties in materials and the identification of interstellar and circumstellar molecules, to practical applications in semiconductor fabrication and fuel combustion.

Experimental work includes Fourier transform spectroscopy, laser ablation of solids, preparation of condensed samples at cryogenic temperatures, and high vacuum techniques. A critical step is testing experimental conclusions about molecular spectra and structures against the predictions of density functional theory (DFT) calculations.

Carbon Chains and Rings
Carbon chains are the backbones of many interstellar molecules. Evidence suggests that the formation of fullerenes starts with the condensation of small cyclic carbon clusters or chains, which eventually form three-dimensional cage structures. Our Fourier transform infrared studies of small carbon clusters formed by laser ablation of graphite and trapped at ~10 K in inert solids have resulted in the first infrared measurements of vibrations for linear Cn (n=12) chains, and the cyclic clusters, C₆ and C₈, generated by a novel laser ablation technique.

On the Identification of the Vibrational Spectrum of Cyclic C₈ in Solid Ar, S.L. Wang, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 112, 1457 (2000).

Fourier Transform Infrared Isotopic Study of the C₁₂ Chain Trapped in Solid Ar, X.D. Ding, S.L. Wang, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 112, 5113 (2000).

Transition Metal-Carbon Clusters
Transition metal-carbon clusters are of interest in the formation of novel nanomaterials, including metcars, and in the catalytic growth of carbon nanotubes. The discovery of simple diatomic molecules containing metals in the circumstellar shells of carbon-rich late stars in which C_n carbon chains have been identified is another reason for our interest in metal-carbon clusters MC_n. FTIR experimental measurements coupled with DFT calculations have enabled the discovery of linear and fan-shaped carbon clusters containing Cr, Ti, Ni, Al, Co, and Sc.

Fourier transform infrared isotopic study of linear CrC₃: Identification of the ν₁(σ) mode, S.A. Bates, C.M.L. Rittby and W.R.M. Graham, J. Chem. Phys. 125, 74506 (2006).

Vibrational spectrum of cyclic TiC3 in solid Ar, R.E. Kinzer, Jr. C.M.L. Rittby, and W.R.M Graham, J. Chem. Phys. 125, 74513 (2006).

Fourier transform infrared observation of the ν₁(σ) mode of linear CoC₃ trapped in solid Ar, S.A. Bates, J.A. Rhodes, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 127, 64506 (2007).

Fourier transform infrared observation of the ν₃(σu) vibration of NiC₃Ni in solid Ar, R.E. Kinzer, Jr., C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 128, 064312 (2008).

FTIR observation and DFT study of the AlC₃ and AlC₃Al linear chains trapped in solid Ar, S.A. Bates, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys, 128, 234301 (2008).

Silicon-carbon Clusters
Mixed silicon-carbon clusters are important for their roles in the formation of interstellar grains and in the deposition of silicon-carbide films. The variety of their geometries also provides an important test for theoretical predictions.

Fourier-transform Infrared Observation of SiCn Chains. II. The ν₁(σ) Mode of Linear SiC₇ in Ar at 10 K, X.D. Ding, S.L. Wang, C.M.L. Rittby, and W.R.M. Graham, J. Phys. Chem. A, 104, 3712 (2000).

Semiconductor Clusters
Efforts to characterize the geometries and electronic structures of small semiconductor clusters have been fueled by their applications to semiconductors. These nanoscale systems also offer the possibility for exploring size dependent effects arising from changes in structure and electronic states.

Vibrational spectra of germanium-carbon clusters. II. GeC7 and GeC9, D.L. Robbins, K.C. Chen, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys., 120, 4664 (2004).

Vibrational spectra of germanium-carbon clusters in solid Ar: Identification of the ν4(σu) mode of linear GeC₅Ge, E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 125, 44504 (2006).

FTIR identification of the 4(σ_u) and ν6(π_u) modes of linear GeC₃Ge trapped in solid Ar, E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham, J. Phys. Chem., in press (2008).